/* Copyright (c) 2010 EPiServer AB
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and
 * to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
 * THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
using System;
using System.Security.Cryptography;
using System.Text;

namespace EPiServer.Municipality.Web {
    /// <summary>
    /// 
    /// </summary>
    /// <remarks></remarks>
    /// <example></example>
    public class Captcha {
        private readonly int _maxSize;
        /* *******************************************************************
		*  Properties
		* *******************************************************************/
        #region public string UniqueKey
        /// <summary>
        /// Gets the UniqueKey of the Captcha
        /// </summary>
        /// <value></value>
        public string UniqueKey {
            get {
                if (string.IsNullOrEmpty(_uniqueKey)) {
                    _uniqueKey = GetUniqueKey(_maxSize);
                }
                return _uniqueKey;
            }
        }
        private string _uniqueKey;
        #endregion
        
        /* *******************************************************************
		*  Constructors
		* *******************************************************************/
        #region public Captcha(int maxSize)
        /// <summary>
        /// Initializes a new instance of the <b>Captcha</b> class.
        /// </summary>
        /// <param name="maxSize"></param>
        public Captcha(int maxSize) {
            _maxSize = maxSize;
        }
        #endregion
        /* *******************************************************************
		*  Methods
		* *******************************************************************/
        #region public static string GetUniqueKey(int maxSize)
        /// <summary>
        /// 
        /// </summary>
        /// <param name="maxSize"></param>
        /// <returns></returns>
        public static string GetUniqueKey(int maxSize) {
            var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789".ToCharArray();
            var data = new byte[1];
            var crypto = new RNGCryptoServiceProvider();
            crypto.GetNonZeroBytes(data);
            data = new byte[maxSize];
            crypto.GetNonZeroBytes(data);
            var result = new StringBuilder(maxSize);
            foreach (byte b in data) {
                result.Append(chars[b%(chars.Length - 1)]);
            }
            return result.ToString();
        }
        #endregion
        /* *******************************************************************
		*  Event methods
		* *******************************************************************/
    }
    #region public static class Base64StringExtensions
    /// <summary>
    /// 
    /// </summary>
    /// <remarks></remarks>
    /// <example></example>
    public static class Base64StringExtensions {
        public static string ToBase64String(this string key) {
            Encoding enc = Encoding.ASCII;
            byte[] bytes = enc.GetBytes(key);
            return Convert.ToBase64String(bytes);
        }
        public static string FromBase64String(this string key) {
            Encoding enc = Encoding.ASCII;
            byte[] bytes = Convert.FromBase64String(key);
            return enc.GetString(bytes);            
        }
    }
    #endregion
}